Bat for baseball or softball and manufacturing method thereof

ABSTRACT

A baseball or softball bat which enables a ball to fly farther than a conventional bat. The bat is made of metal, wood or carbon fiber-reinforced plastic and its cylindrical ball-hitting part has an axial cross section shape as follows: a lot of concave-surfaced grooves and convex-surfaced ridges are arranged in parallel alternately along the circumference of the bat and the convex parts are round and curved outward. The concave and convex parts are covered by a cylindrical sheet of polyurethane elastomer or similar material. Also, a metal baseball or softball bat is manufactured by grooving the cylindrical ball-hitting part surface by a lathe using a roller.

FIELD OF THE INVENTION

The present invention relates to a bat for baseball or softball which enables a ball to fly farther and a manufacturing method thereof.

BACKGROUND OF THE INVENTION

For baseball or softball players, a bat with which enables a ball to fly farther is attractive. For example, in practicing catching, a coach or player hits fungoes repeatedly and when he intends to hit a ball to the outfield, the ball must fly far enough to reach the outfield. For this reason, a team is expected to have, as a fungo bat for rubber-ball baseball, at least one bat with which a ball easily flies far enough.

In the present invention, bats not only include metal bats such as aluminum alloy bats but also bats of easily workable woods and bats of synthetic resin such as carbon FRP. A bat is comprised of a tip part, a ball-hitting part, a tapered part and a grip part. The present invention concerns improvement of the ball-hitting part.

In order to increase the flying distance, it is necessary to decrease deceleration of the bat at the time of collision and increase rebound of the bat. It has long been known that reduction of ball deformation at the moment of hitting is effective as an approach to increasing the rebound. As a means to reduce deformation of the ball at the moment of hitting, a conventional technique that a bat surface is covered by an elastic material has been disclosed (for example, see JP-A No. 2003-019236).

At the moment of hitting, the ball contacts the bat in a surface-to-surface manner and deforms. Therefore, one approach to reducing deformation of the ball is to decrease the area of contact between the ball and the bat. In this sense, to make the surface of the ball-hitting part of the bat uneven is one possible option. As an effort in this direction, in conventional techniques for wooden bats as described in JP-B No. 33 (1958)-001279 and JP-A No. 2002-282405, bumps and dents (concave and convex parts) are made on a bat outer surface by compression forming.

The techniques described in these patent documents are characterized in that bumps and dents are irregularly made on a bat surface. On the other hand, JP-Y No. 36 (1961)-027915 describes a technique that bumps and dents are made in a regular pattern longitudinally. However, this patent document does not disclose any bat manufacturing method and the bat described in the document does not conform to the standards for baseball and softball gear.

As a method of minimizing the possibility of hitting a foul ball or grounder, making bumps and dents transversely may also be thought to be effective. There also exists a conventional technique that grooves and ridges are transversely made in a regular pattern (JP-Y No. 30 (1955)-018934).

In the above technique, grooves and ridges are made spirally. Another document describes a technique of making annular grooves (JP-U No. 53 (1978)-085255).

In the technique described in JP-Y No. 30 (1955)-018934, grooves and ridges are made on the tapered part of the bat as well. However, the tapered part of the bat is not supposed to hit the ball and if the purpose is to increase the flying distance, grooves and ridges should be made only on the ball-hitting part. Also according to JP-U No. 53 (1978)-085255, the top of a ridge between grooves is smooth and flat, so the area of contact with the ball at the moment of hitting cannot be small enough. Therefore, this method is not so effective in reducing deformation of the ball going to fly.

Besides, in the bats as described in JP-Y No. 30 (1955)-018934 and JP-U No. 53 (1978)-085255, grooves and ridges are exposed on their surfaces and the bats do not conform to the standards for baseball and softball gear.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstances and provides a bat which enables a ball to fly farther than conventional bats and conforms to the standards for baseball and softball gear and also provides a manufacturing method thereof.

In order to achieve the above object, according to one aspect of the present invention, there is provided a baseball or softball bat made of metal, wood or carbon fiber-reinforced plastic, wherein in an axial cross section shape of a cylindrical ball-hitting part of the bat, a lot of concave-surfaced grooves and convex-surfaced ridges are arranged in parallel alternately along a circumference of the bat with the convex parts being round and curved outward, and in order to prevent the concave and convex parts from being exposed on a bat surface, the bat surface is covered by a cylindrical rubber, resin or leather sheet.

According to another aspect of the invention, a method of manufacturing a baseball or softball bat of wood or carbon FRP comprises the steps of forming a lot of concave grooves and convex ridges alternately in parallel on a surface of a cylindrical ball-hitting part of the bat excluding a tapered part by cutting with a lathe using an ordinary tool or forming tool or grinding stone, and making the convex parts round and curved outward.

According to a further aspect of the invention, a method of manufacturing a metal baseball or softball bat comprises the steps of forming a lot of concave grooves and convex ridges alternately in parallel on a cylindrical ball-hitting part of the bat in an axial direction by a lathe using a spatula or roller, and making the convex parts round and curved outward.

According to another further aspect of the invention, a method of manufacturing a baseball or softball bat made of synthetic resin such as carbon FRP which uses a die comprises the steps of forming a lot of concave grooves and convex ridges alternately in parallel on a cylindrical ball-hitting part surface of the bat, and making the convex parts round and curved outward.

According to the present invention, the ball-hitting part of the baseball or softball bat has concave and convex curved surfaces and at the moment of hitting a ball, the area where the ball contacts or rebounds is almost linear and the area of contact is smaller, so that ball deformation is reduced and the flying distance is increased.

When the area of contact between the bat and the ball is smaller, friction between the ball and the bat at the moment of hitting is reduced and if the bat hits the ball off its center, slippage is likely to occur, leading to a foul. However, in the present invention, since the surface of the ball-hitting part of the bat is covered by a cylindrical rubber, resin or leather sheet, the problem of reduction in friction between the ball and the bat is resolved and the ball is more likely to fly forward.

In the baseball or softball bat according to the present invention, the cylindrical ball-hitting part has an axial cross section shape that a lot of concave-surfaced grooves and convex-surfaced ridges are arranged in parallel alternately along a circumference of the bat, so the bat is two to three times as stout and durable as conventional bats.

In the baseball or softball bat according to the present invention, the concave and convex parts lie under the rubber, resin or leather sheet wound around the ball-hitting part, so the bat does not give a sense of discomfort and conforms to the standards for baseball and softball gear and enables a ball to fly forward easily.

The baseball or softball bat according to the present invention can be manufactured by an easy process and supplied at low cost if the material is wood or synthetic resin.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more particularly described with reference to the accompanying drawings, in which:

FIG. 1 is a front view showing a wooden fungo bat for rubber-ball baseball and a virtual ball at the moment of hitting;

FIG. 2 is a plan view showing comparison in the area of contact at the moment of hitting between a bat according to the invention and a conventional bat;

FIG. 3 is a sectional view of an aluminum alloy bat for rubber-ball baseball according to the invention;

FIG. 4 is a perspective view of a process of manufacturing a wooden bat for rubber-ball baseball according to the invention by cutting with a lathe using a forming tool;

FIG. 5 is a perspective view of a grooving machine for a wooden bat for rubber-ball baseball according to an embodiment of the invention;

FIG. 6 is a flowchart of a process related to a control program for grooving a wooden bat for rubber-ball baseball according to the invention;

FIG. 7 is a perspective view of a process of manufacturing an aluminum alloy bat for rubber-ball baseball according to the invention by a lathe using rollers;

FIG. 8 is a schematic view of a grooving machine for an aluminum alloy bat for rubber-ball baseball according to the invention;

FIG. 9 is a front view of a rubber-ball baseball bat made of synthetic resin such as carbon FRP;

FIG. 10 is a front view of a rubber-ball baseball bat of synthetic resin such as carbon FRP according to the invention which is integrally molded using a die; and

FIG. 11 is a sectional view showing a bat forming material put in a die.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Next, preferred embodiments of the present invention will be described in detail.

First Embodiment

FIG. 1 is a front view of a wooden fungo bat for rubber-ball baseball according to the present invention and a virtual ball at the moment of hitting. FIG. 2 is a plan view showing comparison in the area of contact at the moment of hitting between the bat according to the invention and a conventional bat.

The bat 1 is comprised of a tip part 2, a ball-hitting part 3, a tapered part 4 and a grip part 5. The ball-hitting part 3 is a larger-diameter part which contacts a ball to hit it far away. In this embodiment, the maximum outside diameter of the ball-hitting part 3 of the bat 1 is 68 mm.

The ball-hitting part 3 has a lot of concave-convex parts 6 transversely formed on it surface. In this embodiment, ten concave-convex parts are formed. These concave-convex parts 6 have a curved sectional shape. Therefore, the curves of their cross sections are longitudinally arranged as symmetrical round curves like a sine curve.

In this embodiment, each concave-convex part 6 consists of a ridge 7 and a groove 8 where the ridge-to-ridge or groove-to groove interval is 15 mm. Hence the total length of the concave-convex parts 6 is 15 cm. The depth 9 of each groove 8 is 3 mm. The depth 9 of each groove 8 should preferably be between 0.5-5 mm and more preferably between 1-5 mm. If the depth should be 0.5 mm or less, at the moment of hitting the ball's bite into the bat would be smaller and its rebound from the bat would be smaller. If the depth should be 5 mm or more, the ball's flight directivity would worsen and the ball-hitting part of the bat would easily break due to hitting impact.

The interval between grooves 8 should preferably be between 10-20 mm and most preferably between 5-20 mm. If the interval should be 5 mm or less, at the moment of hitting the ball's bite into the bat would be smaller and its rebound from the bat would be smaller. If the interval should be 20 mm or more, the ball's bite into the bat at the moment of hitting would be larger and its rebound from the bat would be smaller and the flying distance would be not longer than with a conventional bat with a smooth surface.

FIG. 1 illustrates a virtual ball 10 which dents when hit. Generally the diameter of the ball is 7 cm or so and in this embodiment, it deforms about 4 cm on average, though the amount of deformation depends on ball hardness. Therefore, when the ball 10 is hit, generally peaks of only two ridges (ridge 7 a and ridge 7 b) or at most five ridges of the bat contact the ball 10 (line contact).

Next, comparison is made in contact area (%) against a conventional bat with a smooth ball-hitting part. Shots of a bat at the moment of hitting were taken by a high speed camera (not shown) sideways. FIG. 2 is a plan view obtained by analysis of these shots in enlarged form. In FIG. 2, 11 represents a ball and circle A represents the area of its contact with the conventional bat (surface contact). On the other hand, the bat according to the invention contacts the ball only at peaks of some of its ridges and contact areas 12 are like two small bars (line contact). Table 1 shows the result of an actual hitting test where comparison was made by calculating the ratio (%) of the contact area of the bat according to the invention to the contact area of the conventional bat (100%). Flying distance measurement data indicate the average of flying distances for ten times of hitting.

TABLE 1 Bat Contact Area Flying Distance First Embodiment  32% 94.5 m of the Invention Conventional Bat 100% 87.3 m

The table shows that as compared with the conventional bat, the bat 1 according to the invention reduces the contact area to about one third and increases the flying distance about 18%.

FIG. 3 is a sectional view of an aluminum alloy bat for rubber-ball baseball according to the invention.

The bat 101 is comprised of a tip part 102, a ball-hitting part 103, a tapered part 104 and a grip part 105. The ball-hitting part 103 which does not include the tapered part 103 is a larger-diameter part which contacts a ball to hit it far away. In this embodiment, the maximum outside diameter of the ball-hitting part 103 of the bat 101 is 68 mm.

The uneven surface of the ball-hitting part 103 is covered by a tube 113 of 1.0 mm thick polyurethane elastomer (including no foam) as a covering layer. The tube 113 has the same outside diameter as the tip part 102 and one end of the tapered part 104, and has an even smooth surface. Inside the tube 113 are a lot of concave-convex parts 106 transversely formed on a circumference of a circle of a diameter smaller than the outside diameter (68 mm). In this embodiment, ten concave-convex parts are formed. These concave-convex parts 106 have an arc curved sectional shape. Therefore, the upward and downward curves of their cross sections are arranged as symmetrical round curves like a sine curve.

The covering layer should preferably be a rubber or resin cylindrical sheet of a thickness of 0.5-3.0 mm. If the thickness should be 0.5 mm or less, when the ball collides against the cylindrical sheet of the ball-hitting part, the sheet would stretch and nullify the intended effect of the uneven surface of the ball-batting part; if the thickness should be 3.0 mm or more, the bat would be heavier, resulting in a drop in bat head speed.

In this embodiment, each concave-convex part 106 consists of a ridge 107 and a groove 108 where the ridge-to-ridge or groove-to groove interval is 20 mm. Hence the total length 109 of the concave-convex parts 106 is 20 cm. The depth 109 of each groove 108 is 3 mm. The depth 109 of each groove 108 should preferably be between 0.5-5 mm and more preferably between 1-5 mm. If the depth should be 0.5 mm or less, at the moment of hitting the ball's bite into the bat would be smaller and its rebound from the bat would be smaller. If the depth should be 5 mm or more, the ball's flight directivity would worsen and the ball-hitting part of the bat would easily break due to hitting impact.

The interval between grooves 108 should preferably be between 10-20 mm and most preferably between 5-20 mm. If the interval should be 5 mm or less, at the moment of hitting the ball's bite into the bat would be smaller and its rebound from the bat would be smaller. If the interval should be 20 mm or more, at the moment of hitting the ball's bite into the bat would be larger and its rebound from the bat would be smaller and the flying distance would be not longer than with a conventional bat with a smooth surface.

FIG. 3 illustrates a virtual ball 110 which dents when hit. Generally the diameter of the ball is 7 cm or so and in this embodiment, it deforms about 4 cm on average, though the amount of deformation depends on ball hardness. Therefore, when the ball 101 is hit, generally peaks of only two ridges (ridge 107 a and ridge 107 b) or at most five ridges of the bat contact the ball 110 (line contact).

Next, comparison is made in contact area (%) against a conventional bat with a smooth surface. The method of measuring the contact area (%) is the same as that used for the first embodiment and a detailed explanation thereof is omitted here. Though the contact area is not shown, deformation of the ball occurs when it rebounds upon contact with not the soft covering layer 113 but peaks of ridges 107 a and 107 b of the concave-convex parts 106 under the layer. Table 2 shows the result of an actual hitting test where flying distance measurement data indicate the average of flying distances for ten times of hitting. Measurement data on the conventional bat are shown in Table 1 and omitted here.

TABLE 2 Bat Contact Area Flying Distance Second 38% 93.1 m Embodiment of the Invention

The table shows that as compared with the conventional bat, the bat 101 according to the invention reduces the contact area to about one third and improves the flying distance about 17%.

Third Embodiment

FIG. 4 is a perspective view of a process of manufacturing a wooden bat for rubber-ball baseball according to the present invention by cutting with a lathe using a forming tool.

As shown in FIG. 4, the bat according to the invention is manufactured by cutting work with a contouring tool 50, a lathe which uses so-called forming tools 51. A forming tool 51 with rounded blade tips is selected and using the tool, in an axial cross section shape of the bat, a lot of grooves and ridges are formed alternately in parallel along the circumference of the ball-hitting part and the ridges are rounded outward.

Referring to FIG. 5, a bat fixing device 11 for fixing a bat B is mounted on a base 15 so that it can freely move in horizontal directions a and b and its bat fixing part 12 can turn in directions a and b. The bat support device 13 is intended to support the tip of the bat with its center aligned with the center rotation axis of the bat and can freely move in direction c by means of a drive unit. The forming tool fixing device 14 for fixing the forming tool 51 is mounted on the base 15 and can freely move in directions d and e. A control unit C which controls movement of the forming tool 51 is installed next to the forming tool fixing device 14.

Next, the procedure of forming grooves on the bat will be explained. First, the bat B is fixed by the bat fixing device 11 and the bat support device 13 is moved in direction c to support the bat B. The forming tool fixing device 14 moves in directions d and e to bring the bat B to the vicinity of the forming tool 51. Further the bat B is slightly moved in direction e until its surface touches the forming tool 51; then the bat fixing part 12 turns in direction b to make cuts in the surface of the bat B to form grooves thereon. Taking into consideration the number of blades of the forming tool 51 and the number of grooves to be formed on the surface of the bat B, the forming tool fixing device 14 can be moved in direction d to form as many grooves as needed.

Referring to FIG. 6, the method of creating a control program for grooving a bat will be explained below.

First, at Step 1, bat data such as bat dimensions are stored in a memory. Then, at Step 2, bat groove shape data is extracted. At Step 3, the type of forming tool which is appropriate to the extracted cross section shape data is selected. Then, cutting excursion which determines how to move the selected forming tool is calculated. Then at Step 5 a numerical control program is created according to the calculated cutting excursion and the program is sent to the control unit C for the grooving machine where the bat is grooved.

Fourth Embodiment

FIG. 7 is a perspective view of a process of manufacturing an aluminum alloy bat for rubber-ball baseball according to the present invention by a lathe using rollers.

The abovementioned bat according to the invention can be manufactured by a lathe using rollers 151 of a roller tool 150. A roller tool having circumferentially rounded rollers 151 is selected and using the tool, in an axial cross section shape of the bat, a lot of grooves and ridges are formed alternately in parallel along the circumference of the ball-hitting part and the ridges are rounded outward.

In a grooving machine as shown in FIG. 8, a frame 161 supports a rotary shaft 157 rotatably. A load support roll 155 is provided on one end of the rotary shaft 157 in a way that a bat 153 is suspended by the roll 155. A drive unit 160 is provided on the other end of the rotary shaft 157. Grooves 155′ which fit ridges 151 of a grooving roll 150 are formed on the surface 156 of the load support roll 155 and as shown in FIG. 9, the curvature radius of a groove 155′ is larger than that of the surface 156 of the load support roll 155.

The grooving roll 150, which has ridges arranged along the circumferential direction, is rotatably located in the upper part of the frame 161 through a pressure generator 158. The grooving roll 150 is pressed against the bat 153 by activating the pressure generator 158. Using the pressure gauge 159 of the pressure generator 158, the pressing force is controlled so as to attain a prescribed level and the drive unit 160 is activated to rotate the bat 153 so that annular grooves are formed on the surface of the bat 153. A bat grooving control program is created with the procedure as shown in FIG. 6.

Ridges and grooves can also be formed by machining with a lathe using a spatula.

Fifth Embodiment

FIG. 10 is a front view of a rubber-ball baseball bat made of synthetic resin (carbon FRP) according to a fifth embodiment of the invention.

The bat 201 has a lot of concave-convex parts 206 arranged longitudinally on its ball-hitting part 203. In the case of a synthetic resin bat, since it is manufactured by molding with a die, it is easy to make streaks on it longitudinally. The surfaces of the concave-convex parts 206 are covered by a rubber or resin cylindrical sheet 213 as a covering layer.

As in the case of wooden and metal bats, the concave-convex parts in this embodiment are so formed that the ridge-to-ridge or groove-to groove interval is 20 mm. The total length 203 of the concave-convex parts is 20 cm. The depth of each groove is 3 mm. The depth of each groove should preferably be between 0.5-5 mm and more preferably between 1-5 mm. If the depth should be 0.5 mm or less, the ball's bite into the bat at the moment of hitting would be smaller and its rebound from the bat would be smaller. If the depth should be 5 mm or more, the ball's flight directivity would worsen and the ball-hitting part of the bat would easily break due to hitting impact.

The interval between grooves should preferably be between 10-20 mm and most preferably between 5-20 mm. If the interval should be 5 mm or less, the ball's bite into the bat at the moment of hitting would be smaller and its rebound from the bat would be smaller. If the interval should be 20 mm or more, the ball's bite into the bat at the moment of hitting would be larger and its rebound from the bat would be smaller and the flying distance would be not larger than with a conventional bat with a smooth surface.

The process of manufacturing the bat 201 is as follows: as shown in FIG. 11, a bat forming material (prepreg) of a desired shape, FRP such as resin-impregnated carbon fiber or glass fiber, is put around a bat-shaped iron rod (mandrel). The bat forming material is not limited to carbon fiber and glass fiber but may be other synthetic fibers such as graphite fiber and aromatic polyamide fiber. Thermoplastic resin or thermosetting resin is used as the fiber-reinforced resin and the resin is woven or knitted fiber-reinforced plastic (FRP). Strips of woven or knitted FRP prepreg whose length and width are smaller than the length of the small-diameter part of the bat are formed and successively laid as layers along the whole length of the bat.

Then, the mandrel is released from the prepreg and the prepreg 208 is put in a die 207 which has grooves matched to the shape of a bat with grooves on the surface of its ball-hitting part and compressed air is sent into the inner space 209 of the die to press the bat forming material and form a bat by hot molding. Then, the molded bat is taken out of the die.

An alternative approach is as follows: after the prepreg is put on the mandrel, it is thermally cured by heating and the mandrel is released from the molded workpiece and the surface of the molded workpiece is grooved by cutting. Then, the grooved surface is covered by a rubber or resin cylindrical sheet.

Another method of manufacturing a bat is to use injection-molded thermoplastic FRP or use the filament winding process in which long fiber tows are wound around a bat-shaped mandrel at a prescribed angle and cure and mold them with a die.

The bat thus manufactured according to the invention may be widely used as a fungo bat or a baseball or softball bat. 

1. A baseball or softball bat made of metal, wood or carbon fiber-reinforced plastic, wherein in an axial cross section shape of a cylindrical ball-hitting part of the bat, a lot of concave-surfaced grooves and convex-surfaced ridges are arranged in parallel alternately along a circumference of the bat with the convex parts being round and curved outward; and in order to prevent the concave and convex parts from being exposed on a bat surface, the bat surface is covered by a cylindrical or truncated cone-shaped rubber, resin or leather sheet.
 2. The baseball or softball bat according to claim 1, wherein the concave and convex parts are spaced at internals of 5-20 mm and at the moment of hitting the ball, two to five ridges contact the ball and the depth of the grooves is in the range of 0.5-5.0 mm.
 3. The baseball or softball bat according to claim 1, wherein the baseball bat is a fungo bat.
 4. The baseball or softball bat according to any of claims 1 to 3, wherein outer circumferential surfaces of the concave and convex parts are covered by a cylindrical sheet or net made of 0.5-3.0 mm thick rubber, resin or leather.
 5. A method of manufacturing a wooden baseball or softball bat comprising the steps of: fixing a bat by a bat fixing device; supporting the bat by a cutting support device; moving a cutting fixing device to the vicinity of the bat; inching the fixing device until a cutting tool touches a bat surface; making cuts in the bat by rotation of a bat fixing part; forming a lot of concave grooves and convex ridges alternately in parallel on a cylindrical ball-hitting part surface of the bat by cutting with a lathe with a control unit using an ordinary tool or forming tool or grinding stone; and making the convex parts round and curved outward.
 6. A method of manufacturing a metal baseball or softball bat comprising the steps of: controlling a pressing force using a pressure gauge of a pressure generator to attain a prescribed level; forming a lot of concave grooves and convex ridges alternately in parallel on a surface of a cylindrical ball-hitting part of the bat by activating a drive unit to rotate the bat; and making the convex parts round and curved outward using a spatula or roller.
 7. A method of manufacturing a baseball or softball bat made of synthetic resin such as carbon fiber-reinforced plastic comprising the steps of: putting a bat forming material of a desired shape as a prepreg, FRP such as resin-impregnated carbon fiber or glass fiber, around a bat-shaped iron rod as a mandrel; releasing the mandrel from the prepreg; forming a lot of concave grooves and convex ridges alternately in parallel on a surface of a cylindrical ball-hitting part of the bat; putting the prepreg in a die which has curved surfaces matched to a shape of a bat with round surfaces curved outward; then, sending compressed air into the die to press the bat forming material against the die and form a bat by hot molding; and then, taking a molded bat out of the die. 